1. Field of Invention
The present invention relates to a method and apparatus for adjusting an impeller coupled to a motor in relation to an impeller assembly; and more particularly relates to a method and apparatus for adjusting such an impeller in a close coupled centrifugal pump.
2. Description of Related Art
Internal bushings or shims to set impeller clearance for optimum pump performance are known. However, current devices are difficult to set accurately and reside in the process fluids where they are susceptible to corrosion/erosion. Current methods and apparatus require the user to completely assemble the pump, then insert a feeler gauge into the suction (which is often only 1″ diameter) to set the impeller-to-casing clearance. Then the unit must be disassembled and the appropriate bushing or shims added to the shaft behind the impeller hub. The units are then reassembled and the clearances re-checked. Since gasket and/or o-ring compression can be different at each assembly, this can lead to this process being repeated a multitude of times before it is correct. Due to this complicated process, many times impeller clearances are simply set “close” and hereby cause the pumps to operate under conditions which produce less flow and head as well as consume more energy. Since these bushings/shims are in the process flow, the metallurgy must be selected to be compatible with the pump fluid to avoid corrosion attack, which in many cases is very costly.